U.S. patent number 5,530,421 [Application Number 08/233,867] was granted by the patent office on 1996-06-25 for circuit for automated control of on-board closed circuit television system having side and rear view cameras.
This patent grant is currently assigned to Navistar International Transportation Corp.. Invention is credited to Anthony J. Kraft, Brian P. Marshall.
United States Patent |
5,530,421 |
Marshall , et al. |
June 25, 1996 |
Circuit for automated control of on-board closed circuit television
system having side and rear view cameras
Abstract
An automotive vehicle, such as a tractor-trailer, has a closed
circuit television system that provides the driver with rear and
side views of blind spots that the he or she may otherwise be
unable to see. When the vehicle is placed in reverse, the view from
the rear camera is forced onto the screen of the video monitor to
the exclusion of the side camera, or any other camera connected to
the system. The invention provides an automation circuit that is
responsive to turn signal and hazard warning signal actuation for
causing the side camera to be actively connected to the monitor
screen when the turn signal system is actuated to give a turn
signal to the same side as that viewed by the side video camera and
for preventing the side camera from being actively connected to the
monitor screen when the hazard warning system is actuated to give a
hazard warning signal.
Inventors: |
Marshall; Brian P. (Fort Wayne,
IN), Kraft; Anthony J. (Fort Wayne, IN) |
Assignee: |
Navistar International
Transportation Corp. (Chicago, IL)
|
Family
ID: |
22879002 |
Appl.
No.: |
08/233,867 |
Filed: |
April 26, 1994 |
Current U.S.
Class: |
340/436; 340/435;
348/149 |
Current CPC
Class: |
B60R
1/00 (20130101); B60R 2300/105 (20130101); B60R
2300/70 (20130101); B60R 2300/802 (20130101) |
Current International
Class: |
B60R
1/00 (20060101); B60Q 001/00 () |
Field of
Search: |
;340/436,435,460,461,463
;348/118,148,149 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2465612 |
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Apr 1981 |
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FR |
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0266986 |
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Nov 1928 |
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JP |
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0008729 |
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Jan 1981 |
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JP |
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0209635 |
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Dec 1983 |
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JP |
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0123587 |
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May 1989 |
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JP |
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0164637 |
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Jun 1989 |
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JP |
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0189289 |
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Jul 1989 |
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JP |
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115580 |
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Jun 1969 |
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GB |
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Other References
"Clarion CJ-711F, CJ-720F Car Rearview TV Monitor" Installation
Instructions, Clarion Co. Ltd. .
"Clarion CC-810 Camera/Model: CJ-710 Monitor" Installation Guide
No. 284-4981-01 Clarion Co. Ltd. .
"Clarion CJ-711F, CJ-720F Car Rearview TV Monitor" Owner's
Guide..
|
Primary Examiner: Swarthout; Brent A.
Assistant Examiner: Tong; Nina
Attorney, Agent or Firm: Sullivan; Dennis K.
Claims
What is claimed is:
1. An automotive vehicle comprising operator controls including a
turn signaling system for signaling a right turn by flashing a
right lamp means and a left turn by flashing a left lamp means, a
hazard warning system for signaling a hazard warning by flashing
both said right lamp means and said left lamp means, a gear
selector system for selecting a forward gear to cause a vehicle to
move forward and a reverse gear to cause the vehicle to move in
reverse, and a closed circuit television system comprising a video
monitor comprising a screen in view of an operator and a video
input port, a rear video camera for observing a field of view to
the rear of the vehicle, a side video camera for observing a field
of view to one of the right side and the left side of the vehicle,
a video switch for selectively connecting said video cameras with
said video monitor comprising a first video input port connected
with said rear video camera, a second video input port connected
with said side video camera, and an output video port connected
with said video input port of said monitor, said monitor comprising
an on-off switch for selectively connecting and disconnecting the
monitor to and from a source of electric power for operating the
monitor screen and a mode switch for selecting between a manual
mode of operation and an automatic mode of operation, said video
switch comprising its own mode switch for selecting between a
manual mode of operation and an automatic mode of operation and an
input port-enabling switch associated with said second video input
port of said video switch for selectively enabling said second
video input port of said video switch, characterized by an
automation circuit operatively coupling said turn signaling system,
said hazard warning system, and said gear selector system with said
video switch and said video monitor and comprising means effective
when said mode switch of said monitor is in manual mode, said mode
switch of said video switch is in automatic mode, said on-off
switch of said monitor is on, and said input port-enabling switch
of said video switch that is associated with said second video
input port of said video switch is enabling said second video input
port, for causing said rear video camera to be actively connected
to said monitor screen to the exclusion of said side video camera
whenever said gear selector system is selecting reverse gear
regardless of whether said turn signal system is signaling a turn
or said hazard warning system is giving a hazard warning, for
causing said side video camera to be actively connected to said
monitor screen whenever said turn signal system is signaling a turn
to the same side of the vehicle as the side viewed by said side
video camera provided that reverse gear is not being selected by
said gear selector system, and for preventing said side video
camera from being actively connected to said monitor screen
whenever said hazard warning system is signaling a hazard
warning.
2. An automotive vehicle as set forth in claim 1 in which said
automation circuit comprises a time delay relay that is energized
by the actuation of said turn signal system to indicate a turn to
the same side of the vehicle as the side viewed by said side video
camera provided that reverse gear is not being selected by said
gear selector system, such energization of said time delay relay
providing the application of power to said monitor through said
monitor's on-off switch, said video switch being responsive to the
concurrence of said gear selector system not selecting reverse gear
and said time delay relay being energized to cause the view of said
side video camera to be displayed on said monitor screen.
3. An automotive vehicle as set forth in claim 2 in which said
automation circuit comprises means, effective when said hazard
warning system is actuated to give a hazard warning signal, to
prevent said time delay relay from being energized and consequently
prevent said side video camera from being actively connected to
said monitor screen.
4. An automotive vehicle comprising operator controls including a
turn signaling system for signaling a right turn by flashing a
right lamp means and a left turn by flashing a left lamp means, a
hazard warning system for signaling a hazard warning by flashing
both said right lamp means and said left lamp means, a gear
selector system for selecting a forward gear to cause a vehicle to
move forward and a reverse gear to cause the vehicle to move in
reverse, and a closed circuit television system comprising a video
monitor comprising a screen in view of an operator and a video
input port, a rear video camera for observing a field of view to
the rear of the vehicle, a side video camera for observing a field
of view to one of the right side and the left side of the vehicle,
a video switch for selectively connecting said video cameras with
said video monitor comprising a first video input port connected
with said rear video camera, a second video input port connected
with said side video camera, and an output video port connected
with said video input port of said monitor, characterized by an
automation circuit operatively coupling said turn signaling system,
said hazard warning system, and said gear selector system with said
video switch and said video monitor and comprising means effective
for causing said rear video camera to be actively connected to said
monitor screen to the exclusion of said side video camera whenever
said gear selector system is selecting reverse gear regardless of
whether said turn signal system is signaling a turn or said hazard
warning system is giving a hazard warning, for causing said side
video camera to be actively connected to said monitor screen
whenever said turn signal system is signaling a turn to the same
side of the vehicle as the side viewed by said side video camera
provided that reverse gear is not being selected by said gear
selector system, and for preventing said side video camera from
being actively connected to said monitor screen whenever said
hazard warning system is signaling a hazard warning.
5. An automotive vehicle comprising operator controls including a
turn signaling system for signaling a right turn by flashing a
right lamp means and a left turn by flashing a left lamp means, a
hazard warning system for signaling a hazard warning by flashing
both said right lamp means and said left lamp means, a gear
selector system for selecting a forward gear to cause a vehicle to
move forward and a reverse gear to cause the vehicle to move in
reverse, and a closed circuit television system comprising a video
monitor comprising a screen in view of an operator and a video
input port, a rear video camera for observing a field of view to
the rear of the vehicle, a side video camera for observing a field
of view to one of the right side and the left side of the vehicle,
a video switch for selectively connecting said video cameras with
said video monitor comprising a first video input port connected
with said rear video camera, a second video input port connected
with said side video camera, and an output video port connected
with said video input port of said monitor, characterized by an
automation circuit operatively coupling said turn signaling system,
said hazard warning system, and said gear selector system with said
video switch and said video monitor and comprising means effective
for causing said rear video camera to be actively connected to said
monitor screen to the exclusion of said side video camera whenever
said gear selector system is selecting reverse gear regardless of
whether said turn signal system is signaling a turn or said hazard
warning system is giving a hazard warning, and a time delay relay
that is energized to cause said side video camera to be actively
connected to said monitor screen whenever said turn signal system
is signaling a turn to the same side of the vehicle as the side
viewed by said side video camera provided that reverse gear is not
being selected by said gear selector system, and that is prevented
from being energized whenever said hazard warning system is being
operated to give a hazard warning signal to thereby prevent said
side camera from being actively connected to said monitor screen
whenever said hazard warning system is signaling a hazard warning.
Description
FIELD OF THE INVENTION
This invention relates to automotive vehicles that are equipped
with closed circuit television systems that enable the driver to
view blinds spots that he or she otherwise may be unable to see
when operating the vehicle, particularly side and rear views.
BACKGROUND AND SUMMARY OF THE INVENTION
An example of a vehicle that may advantageously use such a closed
circuit television system is a tractor-trailer in which the driver
sits inside the tractor cab to one side of the vehicle, commonly to
the left side. In the absence of the vehicle being equipped with
such a closed circuit television system, the driver will typically
not enjoy a full field of view either directly to the rear or to
the opposite side from where he or she is seated (i.e., to the
right side when the driver's seat is on the left side), even
assuming that the vehicle is equipped with the usual mirrors. The
obstruction of these views is due largely to the presence of the
trailer behind the tractor and to the fact that the driver sits to
one side of the cab. Equipping such a tractor-trailer with a closed
circuit television system having strategically positioned video
cameras can substantially widen the driver's fields of view to the
rear of the vehicle and to the opposite side from where he or she
is seated.
One presently commercially available closed circuit television
system for a tractor-trailer comprises plural video cameras, one of
which observes a field of view to the rear and another of which
observes a field of view to the opposite side from where the driver
is seated. These two cameras are coupled via respective video
cables with respective video input ports of a video switch that has
a video output port coupled via a video cable with a video input
port of a video monitor inside the cab where the monitor's screen
can be conveniently viewed by the driver. The monitor comprises
certain external controls, one of which is an on-off switch for
turning the monitor screen on and off, and another of which is a
mode switch for selecting either a manual or an automatic mode of
operation. The video switch comprises certain external controls,
including a mode switch for selecting either a manual or an
automatic mode of operation and port-enabling switches associated
with the respective video input ports to which the cameras are
respectively coupled for selectively enabling each respective port.
In addition to the video switch's connections with the cameras and
to the connection of the monitor with the video switch, both the
monitor and video switch have connections with the vehicle's D.C.
electrical system. These connections are to the vehicle's D.C.
power for supplying D.C. power and to the vehicle's back-up light
switch for sensing when the vehicle's transmission is placed in
reverse. Typically, the commercially available system is installed
to allow the driver to select the view from any particular camera,
except that when the vehicle transmission is placed in reverse
gear, as sensed by actuation of the vehicle's back-up light switch
that operates the vehicle's back-up lights, the rear view camera
overrides any other camera selected for display so that the rear
field of view is thus automatically forced onto the monitor
whenever the vehicle is placed in reverse.
One tractor-trailer fleet operator has specified certain additional
criteria for further automated operation of such a closed circuit
television system that will force, or exclude, certain displays on,
or from, the monitor without driver involvement, depending upon not
only gear selection, but also upon turn signal and hazard warning
signal actuation. The commercially available system described above
is incapable of meeting these additional criteria without
modification.
The present invention relates to a circuit for accomplishing such
further automated operation without modification of the components
of the commercially available closed circuit television system
described above. Briefly, the invention satisfies the specified
criteria in a cost-effective manner by a modification that, in a
presently preferred embodiment, involves the addition of only two
relays, two diodes, and related wiring connections. In the case of
vehicles already in service, the modification can be made by tying
into existing wiring harnesses. In the case of new vehicles, the
modifications can be built into the vehicle wiring as original
equipment at the factory, allowing the closed circuit television
system to be installed either at the factory where the vehicle is
built, or later by the customer.
The invention enables the following operations to be automatically
accomplished. 1) The rear video camera will continue to be actively
connected to the monitor to the exclusion of any other video camera
whenever the vehicle is placed in reverse gear regardless of
whether or not a hazard warning or turn signal is being given. 2)
The video camera on the side opposite the driver will be actively
connected to the video monitor to the exclusion of any other video
camera when the turn signal for that opposite side is being given
to signal a turn toward that side, provided that neither reverse
gear nor the hazard warning signal is being selected at the same
time as that turn signal. 3) The video camera on the side opposite
the driver will be prevented from being actively connected to the
monitor whenever the hazard warning signal is being given. In this
way, the monitor will, for a vehicle where the driver sits on the
left side of the cab: 1) be forced to display the rear field of
view when the vehicle is backing up; 2) be forced to display the
right field of view when the vehicle is making a forward right turn
and the hazard warning signal is not being concurrently given; and
3) be incapable of displaying the right field of view whenever a
hazard warning signal is being given.
The foregoing, along with further features, advantages, and
benefits of the invention, will be seen in the ensuing description
and claims which should be considered in conjunction with the
drawing that accompanies this disclosure as an exemplary presently
preferred embodiment of the invention in accordance with the best
mode contemplated for carrying out the invention at this time.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an electrical schematic diagram of a closed circuit
television system of a tractor-trailer in accordance with
principles of the invention .
DESCRIPTION OF THE PREFERRED EMBODIMENT
A known, commercially available closed circuit television system
for a tractor-trailer comprises plural video cameras, such as
cameras 10 and 12, that are coupled with a video switch 14 that is
in turn coupled with a video monitor 16. Camera 10 observes a field
of view to the rear of the tractor-trailer while camera 12 observes
a field of view to the side opposite the side where the driver's
seat is located. Monitor 16 comprises a screen 18 that is disposed
for convenient viewing by the driver when operating the vehicle
from the driver's seat. Where the driver's seat is on the left side
of the vehicle, camera 12 provides a view to the right side, and
this will be the configuration for the exemplary installation in
FIG. 1. The known commercially available 12 volt DC closed circuit
television system for automotive vehicles referred to herein is
known as the Camera & Monitor System [CCMS] available from
Clarion Co. Ltd using Model No. CC-810 Cameras and a Model No.
CJ-711F Car Rearview TV Monitor.
Switch 14 has plural video input ports 20, 22, and 24, and a video
output port 26. Camera 12 comprises a video output port 28 that is
connected to port 20 by means of a video cable 30. Camera 10
comprises a video output port 32 that is connected to port 24 by
means of a video cable 34. Monitor 16 comprises a video input port
36 to which port 26 is connected by means of a video cable 38.
The television system is designed to utilize the existing
electrical system of the vehicle for operating power and for
sensing certain conditions of vehicle operation. Power is supplied
from switch 14 to the cameras 12 and 10 through wiring (not shown)
incorporated in the video cables 30 and 34 respectively while
switch 14 and monitor 16 are connected to the vehicle power supply
in the following manner. The vehicle power supply is nominally +12
VDC relative to ground, and the drawing shows +12 VDC from the
usual ignition branch of the vehicle electrical system being
coupled through a circuit protection device 40 (such as a fuse) to
an input terminal 42 for switch 14. The drawing further shows an
in-line fuse 44 of smaller current rating than device 40 between
terminal 42 and the internal circuitry of switch 14. Another
terminal 46 for switch 14 is connected to ground potential 48.
There are also two additional terminals 50, 52 for switch 14, and
they are associated with automated control of the switch and
monitor when the vehicle is placed in reverse, as will become more
apparent later on.
The drawing shows four terminals 54, 56, 58, 60 associated with
monitor 16. The commercially available monitor has a fifth terminal
(not shown) that is left disconnected for purposes of the present
invention. Terminal 56 is connected to ground potential 48.
Terminal 54 is the positive DC input terminal for receiving the
positive DC potential of the vehicle power supply. Terminal 58 is
connected directly to terminal 52 of switch 14. Terminal 60 is
connected to the vehicle's instrument panel lighting. An in-line
fuse 62 is in the positive feed at terminal 54 for a similar
purpose with respect to the monitor as that of placing fuse 44 in
the feed to switch 14.
The monitor, video switch, and cameras that have been described in
connection with this Description of the Preferred Embodiment are
existing components of the known, commercially available closed
circuit television system described earlier. They are associated
with the vehicle's existing back-up light signal system so that
when the driver places the vehicle transmission in reverse gear,
camera 10 is actively connected to monitor 16 so that the rear
field of view captured by camera 10 is displayed on screen 18 to
the exclusion of any other video camera input.
In addition to the back-up light system, the vehicle is equipped
with certain other conventional systems, including a turn signal
system and a hazard warning signal system. The feature of forcing
the rear view onto the monitor screen when the vehicle is put in
reverse is retained in the present invention, but certain
additional automated functions will be performed automatically
depending upon turn signaling and hazard warning signaling
conditions.
FIG. 1 further shows the vehicle's existing back-up light switch
70, back-up lights 72, 74, an integrated turn signal and hazard
warning switch 76, left turn signal lights 78, and right turn
signal lights 80. It should be appreciated that certain practices
in the automotive industry sometimes integrate multiple functions
into a single assembly, and that is the case for the integrated
turn signal and hazard warning switch 76 which incorporates both
turn and hazard warning switch functions. Also, the illustrated
turn signal lights 78, 80 are used to give both hazard warning and
turn signals. Accordingly, it is to be understood that the
accompanying illustration of the turn signal and hazard warning
circuits discloses one specific configuration that is
representative of a number of alternate, but equivalent,
configurations.
The disclosed embodiment of the invention involves the addition of
a standard relay 82, a time delay relay 84, and two diodes 86, 88,
along with certain wiring accommodations for them. Relay 82
comprises a coil 90 that controls a set of contacts 92. When coil
90 is not energized, contacts 92 are open; when the coil is
energized, the contacts are closed. Coil 90 is connected between
the load side of switch 70 and ground 48. One side of contacts 92
is connected to ground 48 while the opposite side is connected to
two branch circuits. One branch circuit contains diode 86
connecting that opposite side of contacts 92 to a terminal 93 of
switch 76 to which the left turn signal lights 78 are connected;
the other branch circuit is a connection to relay 84.
Relay 84 comprises a time delay coil 94 and a set of contacts 96.
One side of contacts 96 is connected to the load side of device 40;
the other side is connected to a first branch circuit leading
directly to terminal 54 through the in-line fuse 62 and to a second
branch circuit that contains diode 88 connecting that other side of
contacts 96 to the load side of back-up light switch 70. One
terminal of coil 94 connects to the ungrounded side of contacts 92
while the other terminal of coil 94 connects to a terminal 97 of
switch 76 to which the right turn signal lights 80 are
connected.
Operation will now be described for the following combinations of
conditions, it being understood that the construction of switch 76
is such that it is impossible to simultaneously actuate both right
and left turn signal switch portions of switch 76 and that
actuation of the hazard warning switch portion of switch 76 will
produce the same effect as if both right and left turn signal
switch portions were simultaneously actuated:
1) Vehicle in reverse, turn signals off, hazard warning signal
off;
2) Vehicle in reverse, right turn signal on, hazard warning signal
off;
3) Vehicle in reverse, left turn signal on, hazard warning signal
off;
4) Vehicle in reverse, hazard warning signal on;
5) Vehicle not in reverse, turn signals off, hazard warning signal
off;
6) Vehicle not in reverse, right turn signal on, hazard warning
signal off;
7) Vehicle not in reverse, left turn signal on, hazard warning
signal off;
8) Vehicle not in reverse, hazard warning signal on.
Moreover, the following conditions are understood to exist: 1) the
positive vehicle system voltage is applied through protection
device 40 to both one side of contacts 96 of relay 84 and terminal
42 of video switch 14 when the usual vehicle ignition switch is
turned on; 2) the monitor's on-off switch is on and its mode switch
is in manual; and 3) the video switch's mode switch is in
automatic, its port-enabling switches for ports 20 and 24 are on,
and its port-enabling switch for the non-connected port 22 is
off.
Vehicle In Reverse, Turn Signals Off, Hazard Warning Signal Off
Back-up light switch 70 closes when the vehicle transmission is
placed in reverse gear, causing back-up lights 72, 74 to
illuminate. The positive voltage that is conducted by switch 70 to
these lights is also conducted to the ungrounded side of coil 90 of
relay 82, to terminal 50 of video switch 14, and through diode 88
to terminal 54 of monitor 16. Relay 82 thereby operates contacts 92
from open to closed, grounding one side of coil 94 of relay 84.
However, since neither turn nor hazard warning signals are being
given, the opposite side of coil 94 is left floating, and hence
coil 94 remains unenergized, maintaining contacts 96 open.
Because of the positive voltage input to terminal 42 whenever the
ignition switch is on, video switch 14 is able to operate whenever
the ignition switch is on. Power is however selectively applied to
monitor terminal 54 so that screen 18 will be dark when no camera
is being actively connected to monitor 16 by switch 14, and the
purpose in doing this is to avoid an illuminated screen displaying
only "snow" under those circumstances. The closing of switch 70
forces the closed circuit television system to display the field of
view of rear camera 10 on monitor screen 18. This occurs because of
the construction of switch 14, which upon sensing positive system
voltage at terminal 50 causes the rear camera 10 to be actively
connected to monitor 16.
Thus for this set of conditions, the closed circuit television
depicted by FIG. 1 appears to the driver to operate no differently
from the known system described earlier.
Vehicle In Reverse, Right Turn Signal On, Hazard Warning Signal
Off
For descriptive purposes, assume that the system is in the state
that results from the set of conditions just described under
heading 1) where the back-up light switch is closed and the turn
signal and hazard warning signals are off. Actuation of the right
turn signal will now cause positive system voltage to be switched
on and off to coil 94 of relay 84 at the rate at which the flasher
(not shown) flashes the right turn signals. Because relay 84 is a
time delay relay with a delay time longer than the off interval
between turn signal flashes, contacts 96 remain continuously closed
so long as the right turn signal continues to be given. However,
the fact that the right turn signal is being given has no effect on
the closed circuit television system, and consequently, the rear
view from camera 10 continues to be displayed on the monitor
screen. There is a minor effect in the circuit to the extent that
positive system voltage is directly applied to terminal 54 through
contacts 96 rather than through the small voltage drop due to the
presence of diode 88.
Vehicle In Reverse, Left Turn Signal On, Hazard Warning Signal
Off
For descriptive purposes, assume that the system is in the state
that results from the set of conditions described above under
heading 1) where the back-up light switch is closed and the turn
signal and hazard warning signals are off. Actuation of the left
turn signal will have no effect on operation of the closed circuit
television system because diode 86 is poled to block any positive
voltage at terminal 93 from contacts 92 while they are being
grounded.
Vehicle In Reverse, Hazard Warning Signal On
For descriptive purposes, once again assume that the system is in
the state that results from the set of conditions described above
under heading 1) where the back-up light switch is closed and the
turn signal and hazard warning signals are off. Actuation of the
hazard warning switch is equivalent to simultaneously actuating
both the left and right turn signals. It will have no effect on
operation of the closed circuit television system because diode 86
is poled to block any positive voltage at terminal 93 from contacts
92 while they are being grounded, and even though relay 84 is
operating contacts 96 closed, the only change is the slight
increment in positive voltage being applied to terminal 54 due to
by-passing of the feed containing diode 88.
Vehicle Not In Reverse, Turn Signals Off, Hazard Warning Signal
Off
Neither relay is energized, and so the monitor screen is blank.
Vehicle Not In Reverse, Right Turn Signal On, Hazard Warning Signal
Off
None of the connections to coil 90 of relay 82 provides a potential
for energizing it, and so it remains unenergized. However, the
impedance of the left turn lights 78 is sufficiently small in
comparison to the impedance of coil 94 of relay 84 that the
positive potential delivered to coil 94 from terminal 97 due to the
actuation of the right turn signal switch causes a sufficiently
large voltage to be applied across coil 94 to energize it.
Accordingly, contacts 96 are operated to apply the vehicle
electrical system's positive potential to terminal 54 of monitor
16. Because no voltage is being applied to terminal 50 of video
switch 14 due to the fact that back-up light switch 70 is open and
diode 88 is blocking the voltage delivered through the now closed
contacts 96 of relay 84, the video signal that is actively
conducted to monitor 16 is that from the right side camera 12.
Hence, when the vehicle is being operated to make a forward right
turn with the right turn signal being actuated, it is the view to
the right side that is present on screen 18, enabling the driver to
see to the right side of the tractor-trailer.
Vehicle Not In Reverse, Left Turn Signal On, Hazard Warning Signal
Off
Here too, none of the connections to coil 90 of relay 82 provides a
potential for energizing it, and so it remains unenergized. Since
no positive voltage potential is present at terminal 97, coil 94 of
relay 84 remains unenergized, and so screen 18 remains blank.
Vehicle Not In Reverse, Hazard Warning Signal On
Since the positive system potential of the vehicle's electrical
system is being applied in unison to terminals 93 and 97, it is
impossible for any potential difference to be developed across coil
94, and so it remains unenergized. Consequently, screen 18 is
forced to remain blank since contacts 96 cannot be closed to
deliver power to monitor 16 for energizing the screen.
Based on the foregoing description of possible combinations of
operating conditions, it can be seen that the conditions specified
by one fleet operator for displaying particular views on the
monitor screen have been satisfied. Specifically, 1) rear video
camera 10 will continue to be actively connected to monitor 16 to
the exclusion of video camera 12 whenever the vehicle is placed in
reverse gear regardless of whether or not a hazard warning or turn
signal is being given, 2) video camera 12 will be actively
connected to monitor 16 to the exclusion of video camera 10 when
the right turn signal is being given to signal a forward right
turn, provided that neither reverse gear nor the hazard warning
signal is being selected at the same time as the right turn signal,
and 3) video camera 12 will be prevented from being actively
connected to monitor 16 whenever the hazard warning signal is being
given.
While a presently preferred embodiment of the invention has been
illustrated and described, it should be appreciated that principles
are applicable to other embodiments that are equivalent to the
following claims.
* * * * *